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BiologyInhabits lower and middle parts of large rivers, estuaries, coastal lakes and adjacent areas of seas where salinity is lowered by large inflow of freshwater. Can tolerate salinities of up to 12 ppt. Adults mainly prey on planktonic crustaceans, terrestrial insects, and small fish. Larvae and young juveniles feed on zooplankton, algae and insect larvae. Spawns in riffles with heavy current on gravel bottom. There are semi-anadromous and riverine populations. Anadromous populations commence to enter rivers in autumn and move upstream in winter and/or spring. Adults move back to the sea soon after spawning to forage. Young individuals migrate downriver in autumn of same year or the following spring. Hybridizes with Squalius cephalus. All populations sharply declined in the early and middle 20th century due to the constructed dams that hindered in reaching the spawning grounds. Today, spawning occurs only below these dams (Ref. 59043).